Interspinous spacer

ABSTRACT

An implantable spacer for placement between adjacent spinous processes in a spinal motion segment is provided. The spacer includes a body defining a longitudinal passageway. A first arm and a second arm are connected to the body. Each arm has a pair of extensions and a saddle defining a U-shaped configuration for seating a spinous process therein. An actuator assembly is disposed inside the longitudinal passageway and connected to the body. When advanced, the actuator assembly contacts camming surfaces of the arms to rotate them from an undeployed configuration to a deployed configuration. In the deployed configuration, the distracted adjacent spinous processes are seated in the U-shaped portion of the arms providing sufficient distraction to open the neural foramen. An insertion instrument is provided for implanting the interspinous process spacer. The system is configured for implantation through a small percutaneous incision employing minimally invasive techniques.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/923,971 entitled “Interspinous spacer” filed on Apr. 17, 2007 and U.S. Provisional Patent Application Ser. No. 60/923,841 entitled “Spacer insertion instrument” filed on Apr. 16, 2007, each of which is hereby incorporated by reference in its entirety. This application is also a continuation of U.S. patent application Ser. No. 12/148,104 entitled “Interspinous Spacer” filed on Apr. 16, 2008 which is a continuation-in-part of U.S. patent application Ser. No. 11/593,995 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Nov. 7, 2006 which is a continuation-in-part of U.S. patent application Ser. No. 11/582,874 entitled “Minimally invasive tooling for delivery of interspinous spacer” filed on Oct. 18, 2006, now U.S. Pat. No. 8,128,662, which is a continuation-in-part of U.S. patent application Ser. No. 11/314,712 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Dec. 20, 2005, now U.S. Pat. No. 8,152,837, which is a continuation-in-part of U.S. patent application Ser. No. 11/190,496 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Jul. 16, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/079,006 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Mar. 10, 2005, now U.S. Pat. No. 8,012,207, which is a continuation-in-part of U.S. patent application Ser. No. 11/052,002 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Feb. 4, 2005 which is a continuation-in-part of U.S. patent application Ser. No. 11/006,502 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Dec. 6, 2004, now U.S. Pat. No. 8,123,807, which is a continuation-in-part of U.S. patent application Ser. No. 10/970,843 entitled “Systems and methods for posterior dynamic stabilization of the spine” filed on Oct. 20, 2004, now U.S. Pat. No. 8,167,944, all of which are hereby incorporated by reference in their entireties.

FIELD

The present invention generally relates to medical devices, in particular, implants for placement between adjacent interspinous processes of a patient's spine.

BACKGROUND

With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. Typically, with age, a person's ligaments may thicken, intervertebral discs may deteriorate and facet joints may break down—all contributing to the condition of the spine characterized by a narrowing of the spinal canal. Injury, heredity, arthritis, changes in blood flow and other causes may also contribute to spinal stenosis.

Doctors have been at the forefront with various treatments of the spine including medications, surgical techniques and implantable devices that alleviate and substantially reduce debilitating pain associated with the back. In one surgical technique, a spacer is implanted between adjacent interspinous processes of a patient's spine. The implanted spacer opens the spinal canal, maintains the desired distance between vertebral body segments, increases the neural foramen space and as a result, avoids impingement of nerves and relieves pain. For suitable candidates, an implantable interspinous spacer may provide significant benefits in terms of pain relief.

Any surgery is an ordeal. However, the type of device and how it is implanted has an impact. For example, one consideration when performing surgery to implant an interspinous spacer is the size of the incision that is required to allow introduction of the device. Small incisions and minimally invasive techniques are generally preferred as they affect less tissue and result in speedier recovery times. As such, there is a need for interspinous spacers that work well with surgical techniques that are minimally invasive for the patient. The present invention sets forth such a spacer and associated instrumentation.

SUMMARY

According to one aspect of the invention, an implantable spacer for placement between adjacent interspinous processes in a spinal motion segment is disclosed. The spacer includes a body defining a longitudinal passageway and a longitudinal axis. The spacer further includes a first arm and a second arm connected to the body and capable of rotation with respect to the body. Each arm has a pair of extensions and configured for containing a spinous process therein. Each arm has a proximal camming surface. The spacer further includes an actuator assembly connected to the body. The actuator assembly includes an actuator having a proximal end and a distal end. The actuator has at least one bearing surface at the distal end that is configured to engage each camming surface. The actuator is connected to the body and configured to move inside the longitudinal passageway relative to the body to contact each camming surface with the at least one bearing surface and thereby move the arms from an undeployed configuration in which the arms are substantially parallel to the longitudinal axis of the body to a deployed configuration in which the arms are substantially perpendicular to the longitudinal axis of the body to contain adjacent spinous processes when in the deployed configuration.

According to another aspect of the invention, an insertion instrument configured for delivering a spacer to an interspinous process space of a patient and deploying the spacer from an undeployed configuration to at least one deployed configuration to relieve pain is disclosed. The spacer includes a body, at least one arm connected to and movable with respect to the body and a spacer actuator having a proximal end and a distal end disposed at least partially inside the body. The spacer actuator is configured to move the at least one arm from an undeployed configuration to at least one deployed configuration. The insertion instrument includes a handle assembly, a first assembly connected to the handle assembly, a second assembly connected to the handle assembly and a third assembly connected to the handle assembly. The first assembly is configured to connect to the body of the spacer at the distal end of the insertion instrument. The first assembly has a first control at the handle assembly configured to connect and release the body of the spacer and the first assembly. The second assembly is configured to connect to the proximal end of the actuator of the spacer at the distal end of the insertion instrument. The second assembly has a second control at the handle assembly configured to connect and release the actuator and the second assembly. The third assembly is configured to move the second assembly relative to the body of the spacer for arranging the spacer from an undeployed configuration to at least one deployed configuration.

According to another aspect of the invention, a method for implanting a spacer between a superior spinous process and an adjacent inferior spinous process of a patient's spine is disclosed. The method includes the step of providing a spacer. The spacer includes a body having a proximal end, a distal end, and a longitudinal axis. The spacer also includes a first arm and a second arm connected to the body at the distal end. The first and second arms are configured to contain the superior and inferior spinous processes. The spacer further includes an actuator configured to move the first and second arms from a low-profile undeployed configuration in which the first and second arms extend parallel to longitudinal axis to at least one deployed configuration in which the first and second arms are transverse to the longitudinal axis. The method includes the step of inserting the spacer into an interspinous process space from the posterior side of the patient and may be inserted through the superspinous ligament while in the undeployed configuration. The method includes the step of arranging the spacer into at least one deployed configuration.

Other advantages will be apparent from the description that follows, including the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity.

FIG. 1a illustrates a perspective view of a spacer according to the present invention.

FIG. 1b illustrates a side view of a spacer according to the present invention.

FIG. 1c illustrates a top view of a spacer according to the present invention.

FIG. 1d illustrates a cross-sectional view of the spacer of FIG. 1c taken along line X according to the present invention.

FIG. 1e illustrates an end view of a spacer according to the present invention.

FIG. 2a illustrates a perspective view of half of a body of a spacer according to the present invention.

FIG. 2b illustrates a side view of a half of a body of a spacer according to the present invention.

FIG. 2c illustrates a perspective view of another half of a body of a spacer according to the present invention.

FIG. 2d illustrates a side view of the other half of a body of a spacer according to the present invention.

FIG. 3a illustrates a perspective view of a superior arm of a spacer according to the present invention.

FIG. 3b illustrates a side view of a superior arm of a spacer according to the present invention.

FIG. 3c illustrates a perspective view of an inferior arm of a spacer according to the present invention.

FIG. 3d illustrates a side view of an inferior arm of a spacer according to the present invention.

FIG. 4 illustrates a side, semi-transparent view of a spacer in a deployed configuration according to the present invention.

FIG. 5 illustrates a side, semi-transparent view of a spacer in a partially deployed configuration according to the present invention.

FIG. 6 illustrates a side, semi-transparent view of a spacer in a deployed and extended configuration according to the present invention.

FIG. 7a illustrates a perspective view of an actuator assembly of a spacer according to the present invention.

FIG. 7b illustrates a side view of an actuator assembly of a spacer according to the present invention.

FIG. 8 illustrates a side view of an actuator assembly of a spacer according to the present invention.

FIG. 9a illustrates a perspective view of a spacer according to the present invention.

FIG. 9b illustrates a side view of a spacer according to the present invention.

FIG. 9c illustrates a top view of a spacer according to the present invention.

FIG. 9d illustrates a cross-sectional view of the spacer of FIG. 9c taken along line X according to the present invention.

FIG. 9e illustrates an end view of a spacer according to the present invention.

FIG. 10 illustrates a perspective view of a body of a spacer according to the present invention.

FIG. 11a illustrates a perspective view of a superior arm of a spacer according to the present invention.

FIG. 11b illustrates a perspective view of an inferior arm of a spacer according to the present invention.

FIG. 12a illustrates a perspective view of an actuator assembly of a spacer according to the present invention.

FIG. 12b illustrates a side view of an actuator assembly of a spacer according to the present invention.

FIG. 13a illustrates a perspective view of a spacer insertion instrument according to the present invention.

FIG. 13b illustrates a side view of a spacer insertion instrument according to the present invention.

FIG. 13c illustrates a cross-sectional view of a spacer insertion instrument according to the present invention.

FIG. 13d illustrates a perspective view of a clamp shaft of a spacer insertion instrument according to the present invention.

FIG. 14a illustrates side view of a spacer insertion instrument in juxtaposition to a spacer according to the present invention.

FIG. 14b illustrates a top view of a spacer insertion instrument in juxtaposition to a spacer according to the present invention.

FIG. 14c illustrates a cross-sectional view taken along line F-F of FIG. 14a of a spacer insertion instrument in juxtaposition to a spacer according to the present invention.

FIG. 14d illustrates a cross-sectional view taken along line G-G of FIG. 14b of a spacer insertion instrument in juxtaposition to a spacer according to the present invention.

FIG. 15a illustrates a side view of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 15b illustrates a top view of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 15c illustrates a cross-sectional view taken along line G-G of FIG. 15a of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 15d illustrates a cross-sectional view taken along line F-F of a FIG. 15b of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 16a illustrates a side view of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 16b illustrates a top view of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 16c illustrates a cross-sectional view taken along line G-G of FIG. 16a of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 16d illustrates a cross-sectional view taken along line F-F of FIG. 16b of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 17a illustrates a side view of a spacer insertion instrument connected to a spacer in a partially deployed configuration according to the present invention.

FIG. 17b illustrates a top view of a spacer insertion instrument connected to a spacer in a partially deployed configuration according to the present invention.

FIG. 17c illustrates a cross-sectional view taken along line G-G of FIG. 17a of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 17d illustrates a cross-sectional view taken along line F-F of FIG. 17b of a spacer insertion instrument connected to a spacer according to the present invention.

FIG. 18a illustrates a side view of a spacer insertion instrument connected to a spacer in a deployed configuration according to the present invention.

FIG. 18b illustrates a top view of a spacer insertion instrument connected to a spacer in a deployed configuration according to the present invention.

FIG. 18c illustrates a cross-sectional view taken along line G-G of FIG. 18a of a spacer insertion instrument connected to a spacer in a deployed configuration according to the present invention.

FIG. 18d illustrates a cross-sectional view taken along line F-F of FIG. 18b of a spacer insertion instrument connected to a spacer in a deployed configuration according to the present invention.

FIG. 19 illustrates a partial cross-sectional view of a spacer insertion instrument connected to a spacer in a deployed and extended configuration according to the present invention.

FIG. 20 illustrates a spacer according to the present invention deployed in an interspinous process space between two vertebral bodies and a supraspinous ligament.

DETAILED DESCRIPTION

Before the subject devices, systems and methods are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a spinal segment” may include a plurality of such spinal segments and reference to “the screw” includes reference to one or more screws and equivalents thereof known to those skilled in the art, and so forth.

All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

The present invention is described in the accompanying figures and text as understood by a person having ordinary skill in the field of spinal implants and implant delivery instrumentation.

With reference to FIGS. 1a-1e , various views of a spacer 10 according to the present invention are shown. The spacer 10 includes a body 12 connected to a superior extension member or arm 14, an inferior extension member or arm 16, and an actuator assembly 18.

Turning now to FIGS. 2a-2d , the body 12 will now be described. The body 12 is shown to have a clamshell construction with a left body piece 20 (shown in FIGS. 2a and 2b ) joined to a right body piece 22 (shown in FIGS. 2c and 2d ) to capture arms 14, 16 inside. With the right and left body pieces 20, 22 joined together, the body 12 is generally cylindrical. It has a cross-sectional size and shape that allows for implantation between adjacent spinous processes and facilitates delivery into a patient through a narrow port or cannula.

The inside of the body 12 defines an arm receiving portion 24 and an actuator assembly receiving portion 26 with features formed in each of the left and right body pieces 20, 22 that together define the arm and actuator assembly receiving portions 24, 26. In one variation, the arm receiving portion 24 includes slots 28 that receive pins formed on the arms 14, 16 such that the pins rotate and/or translate inside the slots 28. The actuator assembly receiving portion 26 includes a passageway 30. Other features include a tongue 31 a and groove 31 b for mating with the opposite clamshell.

The outside of the body 12 defines a ledge 32 along at least a portion of the periphery. Notches 34 are formed with the ledge 32 at opposite locations as shown in FIG. 1c . The notches 34 are configured for pronged attachment to a spacer delivery instrument and, as seen in FIG. 1c , are of different width to assist the clinician in orienting the spacer 10 with respect to the spacer delivery instrument. When joined together, the left and right body pieces 20, 22 define a proximal opening 36 (as seen in FIG. 1e ) and a distal opening 38 (as seen in FIG. 1a ) in the body 12. A longitudinal scallop (of a type shown in FIG. 10 with reference number 78) extending from the proximal end of the spacer to the distal end on either one or both sides of the body and oppositely located, is formed to facilitate placement of the spacer 10 between and to conform to the anatomy of adjacent interspinous processes.

Turning now to FIGS. 3a and 3b , the superior arm 14 is shown and in FIGS. 3c and 3d , the inferior arm 16 is shown. The superior and inferior arms 14, 16 include pins 40 for mating with the body 12, in particular, for mating with the slots 28 of the arm receiving portion 24. Each of the superior and inferior arms 14, 16 includes at least one camming surface 41, 43, respectively, for contact with the actuator assembly 18. The superior and inferior arms 14, 16 include elongated superior extensions 42 a, 42 b and elongated inferior extensions 44 a, 44 b, respectively. Extensions 42 a and 44 a are located on the left adjacent to the left body piece 20 and extensions 42 b and 44 b are located on right adjacent to the right body piece 22. Superior extensions 42 a, 42 b extend substantially parallel to each other in both an undeployed configuration and in a fully-deployed configuration as do inferior extensions 44 a, 44 b. Extending between extensions 42 a, 42 b is a strut, bridge, bracket or saddle 46 that forms a superior substantially U-shaped configuration together with the extensions 42 a, 42 b that is sized and configured to receive a superior spinous process. As seen in FIG. 3b , the anterior face of the superior extensions 14 includes a slight concavity or curvature 45 for conforming to the bony anatomy of the superior spinous process and or lamina. Also, as seen in FIG. 3d , the anterior face of the inferior extensions 16 includes a slight convexity or curvature 47 for conforming to the bony anatomy of the inferior spinous process and or lamina. Also, extending between inferior extensions 44 a, 44 b is a strut, bridge, bracket or saddle 48 that forms an inferior substantially U-shaped configuration together with the extensions 44 a, 44 b that is sized and configured to receive an inferior spinous process of a spinal motion segment.

The superior and inferior arms 14, 16 are movably or rotatably connected to the body 12, for example by hinge means or the like to provide rotational movement from an undeployed configuration to a deployed configuration that arcs through approximately a 90 degree range or more. The arms 14, 16 are rotationally movable between at least an undeployed, collapsed or folded state (as shown in FIGS. 1a-1e ) and at least a fully deployed state (as shown in FIG. 4). One of many partially deployed states through which the arms move between the fully undeployed and fully deployed state is shown in FIG. 5. In the undeployed state, the arm pairs 14, 16 are aligned generally or substantially axially (i.e., axially with the longitudinal axis defined by the body 12 or to the translation path into the interspinous space of the patient) to provide a minimal lateral or radial profile. The longitudinal axis X of the body is shown in FIG. 1c . In the deployed state, the arm pairs 14, 16 are positioned such that the U-shaped saddles are in a plane or have a U-shaped projection in a plane that is generally or substantially transverse to the longitudinal axis X defined by the body 12 or to the collapsed position or to the translation path into the interspinous space of the patient. The arms 14, 16 may also be linearly moveable or translatable within the plane from a first deployed state to and from a second deployed state characterized by an additional extension of at least one of the arms 14, 16 along the direction of the arrows as shown in FIG. 6. More specifically, the arms 14, 16 can be extended in the general vertical direction along an axis substantially parallel to the spine wherein the arms 14, 16 are extended away from each other and away from the body 12 as denoted by the arrows in FIG. 6. This feature advantageously allows for the most minimally invasive configuration for the spacer without compromising the ability to seat and contain the spinous processes in between levels where the process anatomy in such that the interspinous process space increases in the anterior direction or without compromising the ability of the spacer to provide adequate distraction. The arms 14, 16 are connected to the body 12 and/or to each other in a manner that enables them to be moved simultaneously or independently of each other, as well as in a manner that provides passive deployment and/or vertical extension or, alternatively, active or actuated deployment and/or vertical extension.

Turning now to FIGS. 7a and 7b , the actuator assembly 18 will now be described. The actuator assembly 18 includes an actuator 48 connected to a shaft 50. The actuator 48 includes a distal end 54 and a proximal end 56 and at least two bearing surfaces 58. The bearing surfaces 58 angle towards each other from the proximal end 54 to the distal end 56. The shaft 50 has a substantially reduced cross-sectional area and includes a neck 60 for connection with a spacer insertion instrument. The actuator assembly is at least partially disposed inside the body and is configured for sliding engagement with respect to the body. The actuator 48 includes a slot 61 for receiving an actuator pin 52 seen in FIG. 1d that is connected to the body. The actuator 48, with the pin 52 passed through the slot 61, is connected to the body in sliding engagement. The distal end of the actuator shaft is further configured to engage the superior and inferior arms 14, 16 such that forward translation of the actuator relative to the body effects deployment of the arms into at least one deployed configuration. The at least one deployed configuration can be selectively locked into position via the actuator pin 52 riding inside the slot in the actuator shaft and engaging several fingers 75 forming one or more constrictions along the slot path. The constrictions are configured to lock the pin 52 keeping it fixed in at least one desired deployed configuration in a friction fit engagement. Four sets of fingers 75 grouped in two sets of two oppositely located sets of fingers 75 are shown in FIG. 7b and are configured such that the pin 52 is capable of entering two locked locations between the sets of fingers 75. Typically, a first locked location locks the arms in a deployed configuration and the second locked location locks the arms in an extended-deployed location wherein the pin 52 is resident between two oppositely located sets of fingers when in the at least one locked location. The fingers 75 flex to corral the pin in place.

Another variation of the actuator 48 is shown in FIG. 8. The actuator 48 includes an actuator 48 connected to a shaft 50. The actuator assembly includes a distal end 54 and a proximal end 56 and at least two bearing surfaces 58. The bearing surfaces 58 angle towards each other from the proximal end 54 to the distal end 56. The shaft 50 has a substantially reduced cross-sectional area and includes a neck 60 for connection with a spacer insertion instrument. The actuator includes several fingers 75 forming one or more constrictions along the slot 61 path. The constrictions are configured to lock the pin 52 keeping it fixed in at least one desired deployed configuration in a friction fit engagement. One set of fingers 75 are shown in FIG. 8 and are configured such that the pin 52 is pressed in the fingers when in one deployed configuration.

With reference to FIGS. 9a-9e , various views of another variation of a spacer 10 according to the present invention are shown wherein like reference numbers are used to describe like parts. The spacer 10 includes a body 12, a superior extension member or arm 14, an inferior extension member or arm 16, and an actuator assembly 18.

Turning now to FIG. 10, the body 12 will now be described. The body 12 is shown to have a one-piece construction; however, the body 12 may be configured into a clamshell with two mating pieces joined together as described above. The body 12 has a cross-sectional size and shape that allows for implantation between adjacent spinous processes and facilitates delivery into a patient through a narrow port or cannula.

The inside of the body 12 defines an arm receiving portion 24 and an actuator assembly receiving portion 26 with features formed therein that together define the arm and actuator assembly receiving portions 24, 26. In one variation, the arm receiving portion 24 includes slots 28 that receive one or more pins to capture the arms 14, 16 such that the arms can hinge about the pin. As shown in FIG. 10, the slots 28 are formed in flange-like extensions of the body. The actuator assembly receiving portion 26 includes a passageway 30 that conforms to the shape of the actuator.

Still referencing FIG. 10, the outside of the body 12 defines a ledge 32 along at least a portion of the periphery. Notches 34 (also shown in FIG. 9e ) are formed with the ledge 32 at opposite locations. The notches 34 are configured for pronged attachment to a spacer delivery instrument such that a portion of the spacer delivery instrument securely connects with the body. The body 12 defines a proximal opening 36 and a distal opening 38. A longitudinal scallop 78 extending from the proximal end of the spacer to the distal end on either one or both sides and oppositely located, is formed to facilitate placement of the spacer 10 between and to conform to the anatomy of adjacent interspinous processes. The longitudinal scallops 78 are also shown in FIGS. 9a and 9 e.

Turning now to FIGS. 11a and 11b , there are shown figures of the superior arm 14 and the inferior arm 16, respectively. The superior and inferior arms 14, 16 include apertures 39 for receiving a pin for pinned connection and rotation with respect to the body 12. Each of the superior and inferior arms 14, 16 includes at least one camming surface 41, 43, respectively, for contact with the actuator assembly 18. The superior and inferior arms 14, 16 include elongated superior extensions 42 a, 42 b and elongated inferior extensions 44 a, 44 b, respectively. Extensions 42 a and 44 a are located on one side of the body and extensions 42 b and 44 b are located on the other side of the body. Superior extensions 42 a, 42 b extend substantially parallel to each other in both an undeployed configuration and in a deployed configuration as do inferior extensions 44 a, 44 b. Extending between extensions 42 a, 42 b is a strut, bridge, bracket or saddle 46 that forms a superior substantially U-shaped configuration together with the extensions 42 a, 42 b that is sized and configured to receive and seat or contain at least a portion a superior spinous process. As seen in FIGS. 9b and 11a , the anterior deployed face of the superior extensions 14 includes a slight concavity 45 for conforming to the bony anatomy of the superior spinous process and or lamina. Also, as seen in FIGS. 9b and 11b , the anterior deployed face of the inferior extensions 16 includes a slight convexity 47 for conforming to the bony anatomy of the inferior spinous process and or lamina. Extending between inferior extensions 44 a, 44 b is a strut, bridge, bracket or saddle 48 that forms an inferior substantially U-shaped configuration together with the extensions 44 a, 44 b that is sized and configured to receive and seat at least a portion of an inferior spinous process of a spinal motion segment.

The superior and inferior arms 14, 16 are movably or rotatably connected to the body 12, for example by a pin or hinge means or the like to provide rotational movement to and from an undeployed configuration to a deployed configuration that arcs through approximately a 90 degree range or more. The arms 14, 16 are rotationally movable between at least an undeployed, collapsed or folded state (as shown in FIGS. 9a-9e ) and at least a fully deployed state (as shown in FIGS. 4 and 6). A partially deployed state through which the arms move between the undeployed and deployed state is shown in FIG. 5. In the undeployed state, the arm pairs 14, 16 are aligned generally or substantially axially (i.e., axially with the longitudinal axis defined by the body 12 or to the translation path into the interspinous space of the patient) to provide a minimal lateral or radial profile. The longitudinal axis X of the body is shown in FIG. 9c . In the deployed state, the arm pairs 14, 16 are positioned in a plane generally or substantially transverse to the collapsed position (i.e., in a plane transverse to the longitudinal axis X defined by the body 12 or to the translation path into the interspinous space of the patient). The arms 14, 16 are connected to the body 12 and/or to each other in a manner that enables them to be moved simultaneously or independently of each other, as well as in a manner that provides passive deployment and/or vertical extension or, alternatively, active or actuated deployment and/or vertical extension.

Turning now to FIGS. 12a and 12b , the actuator assembly 18 will now be described. The actuator assembly 18 includes an actuator 48 connected to a shaft 50. The actuator 48 includes a distal end 54 and a proximal end 56 and at least two bearing surfaces 58. The bearing surfaces 58 angle away from each other from the proximal end 54 to the distal end 56. Furthermore, the bearing surfaces are displaced laterally from each other. The shaft 50 has a substantially reduced cross-sectional area forming a neck or receiving portion 60 for connection with a spacer insertion instrument. The actuator assembly 18 is at least partially disposed inside the body and is configured for sliding engagement with respect to the body. The actuator 48 includes a slot 61 for receiving an actuator pin 52 seen in FIGS. 9b and 9d that is connected to the body. The actuator 48, with the pin 52 passed through the slot 61, is connected to the body in sliding engagement. The distal end 54 of the actuator 48 is further configured to engage the superior and inferior arms 14, 16 such that forward translation of the actuator relative to the body 12 effects deployment of the arms 14, 16 into at least one deployed configuration. The at least one deployed configuration can be selectively locked into position via the actuator pin 52 riding inside the slot in the actuator shaft and engaging several fingers 75 forming one or more constrictions along the slot path. The constrictions are configured to lock the pin 52 keeping it and the deployed arms fixed in at least one desired deployed configuration in a friction fit engagement. One set of fingers 75 is shown in FIG. 12b which is configured such that the pin 52 is resident between the fingers when in one deployed configuration.

General assembly of the spacers 10 discussed above will now be described. The arms 14, 16 are disposed in the arm receiving portion 24 of one body piece. The other of the left or right body piece 20, 22 is securely connected/welded to the one body piece thereby capturing the arms 14, 16 inside the arm receiving portion 24 such that the arms 14, 16 are capable of at least rotational movement with respect to the body 12 and in one variation, capable of rotational movement and translation with respect to the body 12. In the variation in which the body 12 is made of one piece, the arms 14, 16 are movably connected to the body 12 with a pin. The actuator assembly 18 is inserted into the passageway 30 of the body 12 and a pin 52 is passed through the body 12 and into the slot 61 of the actuator 48 securing the actuator assembly 18 to the body 12 such that the actuator 48 is allowed to slide with respect to the body 12.

To deliver and deploy the spacer 10 within the patient, the spacer 10 is releasably attached to a delivery instrument at the proximal end of the spacer 10 via notches 34. The delivery instrument will now be described in greater detail.

Turning now to FIGS. 13a-13c , there is shown an insertion instrument 100 according to the present invention. The insertion instrument 100 includes a first subassembly 102, a second subassembly 104 and a third subassembly 105 connected to a handle assembly 106.

The first subassembly 102 is configured to releasably clamp to the body 12 of the spacer 10 at a distal end 108 of the insertion instrument. Still referencing FIGS. 13a-13c , the first subassembly 102 includes a first clamp shaft 110 and a first outer shaft 112 configured for relative motion with respect to one another via a first control 114 located at the handle assembly 106. With particular reference to FIG. 13c , the first control 114 is threaded to the first outer shaft 112 such that rotation of the first control 114 moves the first outer shaft 112 along the longitudinal axis 116 of the insertion instrument 100. Reverse rotation of the first control 114 reverses the direction of translation of the first outer shaft 112. The first clamp shaft 110 is shown in FIG. 13d . The first clamp shaft 110 is a cannulated shaft fixed to the handle assembly 106 and configured to be received inside the cannulated first outer shaft 112. The first clamp shaft 110 includes two oppositely located, outwardly splayed prongs 118 that are permitted to flex inwardly and return to their outwardly splayed normal position as shown in FIG. 13d when released. The prongs 118 are configured to be clamped into the notches 34 formed in the spacer body 12 to clamp onto and securely hold the spacer 10 to the insertion instrument 100. As the first outer shaft 112 is translated distally in sliding motion with respect to the first clamp shaft 110 by rotating the first control 114 in one direction, the first outer shaft 112 is configured to advance over the outwardly splayed prongs 118 and deflect them inwardly to clamp into a properly oriented, juxataposed spacer body 12. When the first outer shaft 112 is translated proximally with respect to the first clamp shaft 110 by rotating the first control in an opposite direction, the first outer shaft 112 is configured to uncover the prongs 118 allowing them to flex outwardly to their normal outwardly splayed configuration to release a spacer 10 to which it is connected.

The second subassembly 104 is configured to releasably clamp to the actuator 48 of the spacer 10 at the distal end 108 of the insertion instrument 100. The second subassembly 104 includes a second clamp shaft 120 and a second outer shaft 122 configured for relative motion with respect to one another via a second control 124 located at the handle assembly 106. The second control 124 is threaded to the second outer shaft 122 such that rotation of the second control 124 moves the second outer shaft 122 along the longitudinal axis 116 of the insertion instrument 100. Reverse rotation of the second control 124 reverses the direction of translation of the second outer shaft 122. The second clamp shaft 120 is shown in FIG. 13c and is similar to the first clamp shaft 110 except that it is positioned approximately 90 degrees with respect to the first clamp shaft 110. The second clamp shaft 120 is a connected to the third subassembly 105 and configured to be received inside the cannulated second outer shaft 122. Both the second clamp shaft 120 and the second outer shaft 122 are located concentrically inside the first clamp shaft 110. The second subassembly 104 is located concentrically inside the first subassembly 102. The second clamp shaft 120 includes two oppositely located, outwardly splayed prongs 126 that are permitted to flex inwardly and return to their outwardly splayed normal position. The prongs 126 are configured to be clamped to the actuator 48 of the spacer 10, and in particular, to the proximal end 56 of the actuator 48 at the neck receiving portion 60 of the actuator shaft 50. Any suitable interface may be formed for connecting to the actuator 48. As the second outer shaft 122 is translated distally with respect to the second clamp shaft 120 by rotating the second control 124 in one direction, the second outer shaft 112 is configured to advance over the outwardly splayed prongs 126 and deflect them inwardly to connect to the actuator 48 of a juxataposed spacer 10. When the second outer shaft 122 is translated proximally with respect to the second clamp shaft 120 by rotating the second control 124 in an opposite direction, the second outer shaft 122 is configured to uncover the prongs 126 allowing them to flex outwardly to their normal outwardly splayed configuration to release the actuator 48 of the spacer 10 to which it is connected.

The third subassembly 105 is configured to translate the entire second subassembly 104 with respect to the handle assembly 106 (or, in another variation, with respect to the first subassembly 102) to thereby translate the actuator 48 of a spacer 10 with respect to the body 12 of the spacer to arrange the spacer to and from deployed and undeployed configurations. The third subassembly 105 includes a proximally located third control 128 configured in the form of a removable drive handle threaded to the second assembly 104 and configured for effecting relative motion of the second assembly 104 with respect to the handle assembly 106 wherein rotation of the drive handle 128 moves the second assembly 104 along the longitudinal axis 116 of the insertion instrument 100. Reverse rotation of the drive handle 128 reverses the direction of translation of the second assembly 104. Because the second assembly 104 is connected to the actuator 48 of the spacer 10 such longitudinal translation effects translation of the actuator 48 with respect to the body 12 of the spacer 10. In one variation, the third assembly 105 further includes a fourth control 130 for adjusting the position of the second assembly 104 relative to the handle assembly 106 such that differently-sized spacers are easily connectable to the insertion instrument at the distal end. For example, as shown in FIG. 13b , a setting of large L on the fourth control 130 positions the second assembly 104 proximally with respect to the handle assembly 106 such that a spacer with a longitudinally longer body 12 may be easily accepted and connected to the insertion instrument 100 at the distal end 108. A setting of small S on the fourth control 130 positions the second assembly 104 distally with respect to the handle assembly 106 such that a spacer with a longitudinally shorter body 12 may be easily accepted and connected to the insertion instrument 100 at the distal end 108. The fourth control 130 may also be employed simultaneously or independently of the third control 128 to arrange the spacer to and from deployed and undeployed configurations.

Other features of the insertion instrument 100 include a lock 132 configured to lock the first and second subassemblies 102, 104 into position to prevent accidental release of the spacer body 12 or spacer actuator 12. A direction indicator 134 is provided on the instrument 100 for orientating the instrument 100 with respect to the patient anatomy. In one variation, for example, the direction indicator 134 indicates a cephalad orientation. Various depth markings 136 are also provided as well as connection arrows for lining up the spacer with respect to the instrument.

Turning now to FIGS. 14a-14d , the operation of the spacer 10 and insertion instrument 100 will now be discussed. In operation, the fourth control 130 is adjusted for the size of spacer 10 to be connected to the insertion instrument 100. If a longitudinally large spacer 10 is to be connected, the fourth control 130 is set to large. If a longitudinally small spacer 10 is to be connected, the fourth control 130 is set to small. This selection positions the distal end of the second assembly 104 proximally or distally with respect to the distal end 108 of the instrument 10 for attachment to the actuator 48. The spacer 10 is then positioned proximate to the distal end 108 of the insertion instrument 100. The spacer 10 is provided or otherwise placed in its undeployed state next to the distal end 108 of the instrument. Initially, the prongs 118, 126 are not engaged as shown in FIGS. 14a -14 d.

Turning now to FIGS. 15a-15d , the first control 114 is activated at the handle of the insertion instrument 100 such that the first subassembly 102 is connected to the body 12 of the spacer 10. The first control 114 is rotated in one direction to advance the first outer shaft 112 over the first clamp shaft 110 deflecting the prongs 118 inwardly into the notches 34 on the body of the spacer 12 to secure the spacer body 12 to the instrument as shown clearly in FIG. 15c . FIG. 15d shows that the prongs 126 of the second subassembly 104 are not connected to the actuator 48.

Turning now to FIGS. 16a-16d , the second control 124 is activated at the handle of the insertion instrument such that the second subassembly is connected to the actuator 48 of the spacer 10. The second control 124 is rotated in one direction to advance the second outer shaft 122 over the second clamp shaft 120 deflecting the prongs 126 inwardly to clamp onto the proximal end 56 of the actuator shaft 50 to secure the actuator 48 to the instrument 100 as shown clearly in FIG. 16d . Although described such that the first subassembly 102 is first connected to the body 12, the instrument 100 may be employed such that the second subassembly 104 is connected first to the actuator and then the first subassembly 102 is connected to the body. With both the first and second subassemblies 102, 104 connected to the spacer 10, the lock 132 is pushed to lock the first and second subassemblies 102, 104 in place to prevent accidental detachment.

To deliver and deploy the spacer 10 within the patient, the spacer 10 is releasably attached to a delivery instrument 100 at the proximal end of the spacer 10 as described. A small midline or lateral-to-midline incision is made in the patient for minimally-invasive percutaneous delivery. In one variation, the supraspinous ligament is split longitudinally along the direction of the tissue fibers to create an opening for the instrument. Dilators may be further employed to create the opening. In the undeployed state with the arms 14, 16 in a closed orientation and attached to a delivery instrument, the spacer 10 is inserted into a port or cannula, if one is employed, which has been operatively positioned in an interspinous space within a patient's back and the spacer is passed through the cannula to the interspinous space between two adjacent vertebral bodies. The spacer 10 is advanced beyond the end of the cannula or, alternatively, the cannula is pulled proximately to uncover the spacer 10 connected to the instrument 100. Once in position, the third control 128 and/or fourth control 130 is rotated to begin the deployment of at least one of the superior arm 14 and inferior arm 16 or both simultaneously. FIGS. 17a-17d illustrate the superior arm 14 and the inferior arm 16 in a partially deployed position with the arms 14, 16 rotated away from the longitudinal axis 116 and the second subassembly 104 advanced distally with respect to the body of the spacer 12. Distal advancement of the second subassembly 104 which is connected to the actuator 48, in turn, distally advances the actuator 48 whose bearing surfaces 58 contact the superior and inferior camming surfaces 41, 43 pushing the superior and inferior arms 14, 16 into rotation about the pins 40. The position of the arms 14, 16 in FIGS. 17a-17d may be considered to be one of many partially deployed configurations that are possible and from which the deployment of the arms 14, 16 is reversible with opposite rotation of the third and/or fourth controls 128, 130.

Turning to FIGS. 18a-18d , there is shown an insertion instrument 100 connected to a spacer 10 in a first deployed configuration in which the arms 14, 16 are approximately 90 degrees perpendicular to longitudinal axis 116 or perpendicular the initial undeployed configuration. Continued rotation of third and fourth controls 128, 130 moves the second subassembly 104 further distally with respect to the body 12 of the spacer 10 pushing the bearing surfaces 58 further against the superior and inferior camming surfaces 41, 43. While in the first deployed configuration, the clinician can observe with fluoroscopy the positioning of the spacer 10 inside the patient and then choose to reposition the spacer if desired. Repositioning of the spacer may involve undeploying the arms 14, 16 rotating them into any one of the many undeployed configurations. The spacer may then be re-deployed into the desired location. This process can be repeated as necessary until the clinician has achieved the desired positioning of the spacer in the patient.

Even further advancement of the second subassembly 104 from the first deployed configuration results in the spacer assuming a second deployed configuration shown in FIG. 19. The second deployed configuration is an extended configuration in which the superior and inferior arms 14, 16 extend transversely with respect to the longitudinal axis 116 outwardly in the direction of the arrows in FIG. 19. Such extension is guided by the length and shape of the slots 28 in which the arms 14, 16 move. Once deployed, the superior arm 14 seats the superior spinous process and the inferior arm 16 seats the adjacent inferior spinous process. Such extension may also provide some distraction of the vertebral bodies. As seen in this deployed configuration shown in FIG. 19, the actuator pin 52 is seated between the fingers 75 and locked therein.

Following deployment, the lock 132 is released to permit rotation of the first and second controls 114, 124 which are rotated in the opposite direction to release the body 12 and the actuator 48 from the instrument 100, respectively. The insertion instrument 100, thus released from the spacer, is removed from the patient leaving the spacer 10 implanted in the interspinous process space as shown in FIG. 20. In FIG. 20, the spacer 10 is shown with the superior arm 14 seating the superior spinous process 138 of a first vertebral body 142 and the inferior arm 16 seating the inferior spinous process 140 of an adjacent second vertebral body 144 providing sufficient distraction to open the neural foramen 146 to relieve pain. As mentioned above, the shape of the superior arm 14 is such that a superior concavity or curvature 45 is provided to conform to the widening of the superior spinous process 138 in an anterior direction toward the superior lamina 148 going in the anterior direction. In general, the superior arm 14 is shaped to conform to anatomy in the location in which it is seated. Likewise, as mentioned above, the shape of the inferior arm 16 is such that an inferior convexity or curvature 47 is provided to conform to the widening of the inferior spinous process 140 in an anterior direction toward the inferior lamina 150. The supraspinous ligament 152 is also shown in FIG. 20.

Any of the spacers disclosed herein are configured for implantation employing minimally invasive techniques including through a small percutaneous incision and may or may not be through the supraspinous ligament. Implantation through the supraspinous ligament involves selective dissection of the supraspinous ligament in which the fibers of the ligament are separated or spread apart from each other in a manner to maintain as much of the ligament intact as possible. This approach avoids crosswise dissection or cutting of the ligament and thereby reduces the healing time and minimizes the amount of instability to the affected spinal segment. While this approach is ideally suited to be performed through a posterior or midline incision, the approach may also be performed through one or more incisions made laterally of the spine with or without affect to the supraspinous ligament. Of course, the spacer may also be implanted in a lateral approach that circumvents the supraspinous ligament altogether.

Other variations and features of the various mechanical spacers are covered by the present invention. For example, a spacer may include only a single arm which is configured to receive either the superior spinous process or the inferior spinous process. The surface of the spacer body opposite the side of the single arm may be contoured or otherwise configured to engage the opposing spinous process wherein the spacer is sized to be securely positioned in the interspinous space and provide the desired distraction of the spinous processes defining such space. The additional extension of the arms) subsequent to their initial deployment in order to seat or to effect the desired distraction between the vertebrae may be accomplished by expanding the body portion of the device instead of or in addition to extending the individual extension members 14, 16. In another variation, the spacer is configured such that arms are bifurcated side-to-side, instead of top-to-bottom for independent lateral deployment. For example in such a variation, the spacer includes a left arm and a right arm, instead of a superior arm and an inferior arm. The right arm includes extensions 42 a and 44 a and the left arm includes extensions 42 b and 44 b wherein extensions 42 a and 44 b are deployed independently of extension 42 b, 44 b on the other side of the spacer. This variation allows for the spacer to be inserted in the same manner as described above and one arm is deployed on one side of the both the superior and inferior spinous processes and the second arm is subsequently deployed on the other side of both the superior and inferior spinous processes.

The extension arms of the subject device may be configured to be selectively movable subsequent to implantation, either to a fixed position prior to closure of the access site or otherwise enabled or allowed to move in response to normal spinal motion exerted on the device after deployment. The deployment angles of the extension arms may range from less than 90 degrees (relative to the longitudinal axis defined by the device body) or may extend beyond 90 degrees. Each extension member may be rotationally movable within a range that is different from that of the other extension members. Additionally, the individual superior and/or inferior extensions 42 a, 42 b, 44 a, 44 b may be movable in any direction relative to the strut or bridge extending between an arm pair or relative to the device body in order to provide shock absorption and/or function as a motion limiter, or serve as a lateral adjustment particularly during lateral bending and axial rotation of the spine. The manner of attachment or affixation of the extensions to the arms may be selected so as to provide movement of the extensions that is passive or active or both. In one variation, the saddle or distance between extensions 42 a and 42 b or between 44 a and 44 b can be made wider to assist in seating the spinous process and then narrowed to secure the spinous process positioned between extensions 42 a and 42 b or between 44 a and 44 b.

The preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims. 

We claim:
 1. An implantable interspinous spacer for engaging adjacent spinous processes of a subject, the implantable interspinous spacer comprising: a body defining a passageway; arms connected to the body, each arm having a pair of extensions spaced apart from one another to define an opening, wherein the arms are rotatable with respect to the body such that the arms move from an undeployed configuration for inserting the implantable interspinous spacer between the spinous processes to a first deployed configuration for positioning each spinous process within one of the openings between the extensions, and wherein the arms are linearly movable with respect to the body such that the arms move from the first deployed configuration to a second deployed configuration for distracting the spinous processes; and an actuator assembly configured to deploy the arms and comprising an actuator, wherein the actuator is movable along the passageway to rotate the arms from the undeployed configuration to the first deployed configuration and to linearly move the arms from the first deployed configuration to the second deployed configuration.
 2. The implantable interspinous spacer of claim 1 wherein the actuator includes a proximal end, a distal end, at least one bearing surface at the distal end, wherein the at least one bearing surface is configured to engage caroming surfaces of the arms when the actuator moves along the passageway to cause the arms to roll along the at least one bearing surface such that the arms move from the undeployed configuration toward the first deployed configuration, and wherein each arm has a substantially flat surface for contacting the at least one bearing surface when the arms are in the first deployed configuration.
 3. The implantable interspinous spacer of claim 1 wherein the arms in the undeployed configuration are substantially parallel to a longitudinal axis of the body, and wherein the arms in the first deployed configuration are substantially perpendicular to the longitudinal axis of the body.
 4. The implantable interspinous spacer of claim 1 wherein the actuator is movable along the passageway to cause the arms to rotate from the undeployed configuration to the first deployed configuration, and the actuator is further movable along the passageway to push the arms away from each other toward the second deployed configuration.
 5. The implantable interspinous spacer of claim 1 wherein at least one of the arms includes a first pin positioned in a first slot in the body and defining an axis of rotation about which the at least one arm rotates to move from the undeployed configuration to the first deployed configuration, and a second pin positioned in a second slot in the body and movable along the second slot to move the arm from the undeployed configuration and the second deployed configuration.
 6. The implantable interspinous spacer of claim 1 wherein each arm rotates approximately 90 degrees when that arm moves from the undeployed configuration to the first deployed configuration.
 7. The implantable interspinous spacer of claim 1 wherein each arm is configured to rotate outwardly into a planar space that is substantially transverse to a longitudinal axis of the body, and wherein each arm is configured to translate in the planar space away from the longitudinal axis when the arm moves from the first deployed configuration toward the second deployed configuration.
 8. The implantable interspinous spacer of claim 1 wherein the actuator includes two bearing surfaces that converge towards a distal end of the actuator, and wherein each bearing surface is positioned to contact and move one of the arms.
 9. The implantable interspinous spacer of claim 1 wherein a proximal end of the actuator assembly is configured for attachment to an instrument capable of causing movement of actuator with respect to the body.
 10. The implantable interspinous spacer of claim 1 wherein each of the openings is configured to receive one of the spinous processes such that the extensions are located on opposite sides of the spinous process.
 11. The implantable interspinous spacer of claim 1 wherein the actuator is linearly movable along the passageway so as to push the arms away from one another to translate the arms outwardly a sufficient distance to distract the spinous processes.
 12. The implantable interspinous spacer of claim 1 wherein the actuator assembly is configured to begin linearly moving the arms after the arms have rotated from the undeployed configuration to the deployed configuration.
 13. The implantable interspinous spacer of claim 1 wherein the arms include a first arm and a second arm, wherein the first arm is linearly movable in a first direction when the first arm moves toward the second deployed configuration, and wherein the second arm is linearly movable in a second direction generally opposite the first direction when the second arm moves toward the second deployed configuration.
 14. An implantable spacer for distracting adjacent spinous processes of a subject, the implantable spacer comprising: a spacer body defining a passageway; arms coupled to the spacer body and each arm including a pair of extensions spaced apart from one another to define an opening between the extensions; and an actuator assembly in the passageway and operable to cause the arms to rotate from an undeployed configuration for delivering the implantable spacer between the spinous processes toward a deployed configuration for positioning spinous processes in the openings, and wherein the actuator assembly is operable to translate the arms relative to the spacer body such that the arms move linearly from the deployed configuration to a distracted configuration for distracting the spinous processes positioned in the openings.
 15. The implantable spacer of claim 14 wherein the actuator assembly includes an actuator with a tapered head, and wherein the actuator is linearly movable along the passageway to cause the arms to roll along the tapered head as the arms rotate from the undeployed configuration to the deployed configuration.
 16. The implantable spacer of claim 14 wherein the arms have camming surfaces and locking surfaces, wherein the camming surfaces roll along a tapered head of the actuator assembly when the tapered head moves linearly along the passageway and the arms move toward the deployed configuration, and wherein the locking surfaces engage the tapered head when the arms are in the distracted configuration.
 17. The implantable spacer of claim 14 wherein the arms in the undeployed configuration are substantially parallel to a longitudinal axis of the spacer body, and wherein the arms in the deployed configuration are substantially perpendicular to the longitudinal axis of the spacer body.
 18. The implantable spacer of claim 14 wherein the arms include a first arm and a second arm, wherein the first arm includes a first pin positioned in a first slot in the spacer body and about which the extensions of the first arm rotate when the first arm moves from the undeployed configuration toward the deployed configuration, and a second pin positioned in a second slot in the spacer body and movable along the second slot to move the first arm toward the deployed configuration.
 19. The implantable spacer of claim 14 wherein the actuator assembly is connected to the spacer body and is configured to mechanically drive the arms from the undeployed configuration to the distracted configuration in response to operation of the actuator assembly.
 20. The implantable spacer of claim 14 wherein the arms are U-shaped.
 21. The implantable spacer of claim 14 wherein each of the openings is configured to receive one of the spinous processes such that the extensions are located on opposite sides of the spinous process.
 22. The implantable spacer of claim 14 wherein the actuator assembly has a linearly movable actuator configured to push the arms away from one another to translate the arms a sufficient distance to distract the spinous processes when the actuator moves through the passageway.
 23. The implantable spacer of claim 14 wherein the actuator assembly is configured to begin translating the arms after the arms have rotated from the undeployed configuration to the deployed configuration.
 24. The implantable spacer of claim 14 wherein the actuator assembly is configured to begin linearly moving the arms after the arms have rotated from the undeployed configuration to the deployed configuration.
 25. An implantable spacer for distracting adjacent spinous processes of a subject, the implantable spacer comprising: a spacer body defining a passageway; arms coupled to the spacer body and each arm including a pair of extensions spaced apart from one another to define an opening between the extensions, wherein the arms include a first arm and a second arm, wherein the first arm includes a first pin positioned in a first slot in the spacer body and about which the extensions of the first arm rotate when the first arm moves from the undeployed configuration toward the deployed configuration, and a second pin positioned in a second slot in the spacer body and movable along the second slot to move the first arm toward the deployed configuration, wherein the second slot has an arcuate section and a linear section, wherein the second pin moves along the arcuate section when the first arm rotates toward the deployed configuration, and wherein the second pin moves along the linear section when the first arm moves toward the distracted configuration; and an actuator assembly in the passageway and operable to cause the arms to rotate from an undeployed configuration for delivering the implantable spacer between the spinous processes toward a deployed configuration for positioning spinous processes in the openings, and wherein the actuator assembly is operable to drive the arms from the deployed configuration to a distracted configuration for distracting the spinous processes positioned in the openings.
 26. The implantable spacer of claim 25 wherein the actuator assembly pushes the first and second arms away from each other when the first and second arms move toward the distracted configuration.
 27. An implantable interspinous spacer for engaging adjacent first and second vertebrae of a subject, comprising: a body; first and second arms each rotatable with respect to the body to move from a delivery configuration to a rotated configuration for engaging the first and second vertebrae, and wherein the first and second arms are linearly movable with respect to the body to move from the rotated configuration to a distraction configuration; and an actuator movable along the body to rotate the first and second arms toward the rotated configuration and to linearly move the first and second arms toward the distracted configuration.
 28. The implantable interspinous spacer of claim 27, wherein the actuator moves linearly along a passage in the body to drive the first and second arms away from the delivery configuration. 